In the first minutes of writer-director David Ayer’s Fury, about American soldiers slogging through Europe in the final days of World War II, Brad Pitt, as tanker Don Collier, slides his knife behind the eye of a German lieutenant.

“Piercing his brainpan with a CRACK,” is how Ayer’s screenplay describes the move. (In Dolby Digital sound, it will be a very loud crack.) Pitt, our hero, then calmly wipes his blade clean on the German’s uniform.

The Good War this is not.

In what promises to be one of the most daring studio movies in an awards season that will bring several World War II films, Ayer, Pitt and a band of producers backed by Sony Pictures Entertainment are poised to deliver what the popular culture has rarely seen. That is, a relentlessly authentic portrayal — one stuntman was run through with a bayonet on the set — of the extremes endured, and inflicted, by Allied troops who entered Germany in the spring of 1945.

Quentin Tarantino’s Inglorious Basterds, which also starred Pitt, was brutal but surreal. Few believed that a real-life counterpart to his Lt Aldo Raine had collected Nazi scalps by the hundred.

The first 20 minutes of Steven Spielberg’s Saving Private Ryan came much closer to what Ayer calls the war’s “ground truth”. But little in its portrayal of slaughter at Normandy hinted at what some American soldiers would do less than a year later in their final push to victory — yes, they executed prisoners and killed armed children.

Ayer, a studio writer (Training Day) and indie film director (End of Watch), had been meditating for years on the Fury screenplay, but he wrote it in a burst about 18 months ago. The resulting movie, Ayer said, was intended both as a personal journey and as a correction to the pop cultural record.

On the personal front, Fury is meant to unlock the psychology of Ayer’s older relations, who fought but seldom spoke of it. And the film trades on his own military experience as a sonar operator on an attack submarine in the 1980s.

The time also seemed right for an honest look at those who were fighting and dying in ferocious encounters even as the German surrender was imminent, he said. “There is a lot of contemporary parallel here,” Ayer said, referring to soldiers who confront death in Afghanistan, for instance, even as US engagement there is supposed to be ending.

Their problem is that of Pitt’s character, known as Wardaddy, and the four tankers — portrayed by Logan Lerman, Shia LaBeouf, Michael Peña and Jon Bernthal — whom he has pledged to keep alive, Ayer said.

American tank casualties during the war in Europe were horrific. The 3rd Armored Division landed at Normandy with 232 M4 Sherman medium tanks, the Army’s primary armoured weapon. But it had 648 tanks destroyed, and another 700 knocked out. The armour was too thin, and the tanks were prone to burn when hit even by a hand-held panzerfaust anti-tank weapon. Crews were incinerated, and often listed as missing, not killed, because they left no remains.

“Henry Ford built the Sherman. Ferdinand Porsche built the Tiger (the better-armoured German tank),” said Bill Block, a producer whose QED International assembled and financed Fury.

Many tankers, assured of the Sherman’s strength in training, only learned otherwise in combat. “Seeing our mounting tank losses made me realise that our armoured forces had been the victims of a great deceit,” Belton Y Cooper, a veteran of the tank war, wrote in the book Death Traps, one of many sources Ayer consulted.

In Ayer’s story, the crew of a tank called Fury, one of about 10 real Shermans used in the film, have fought their way from Africa, to Normandy, across the Rhine and into Germany.

Ragged, worried and, in the case of Peña’s Trini Garcia, almost always drunk, they can see the war’s end. But they can’t quite reach it.

As the movie opens, they are preparing to scrape the remains of a headless buddy from the bow gunner’s seat. “I sure didn’t keep him alive,” Pitt mutters.

Much of what his Wardaddy does may shock viewers who have watched American soldiers behave brutally in Vietnam War films at least since Apocalypse Now, but have rarely seen ugliness in the heroes of World War II.

In his harsh initiation of a new gunner, Pitt’s character crosses lines, both legal and moral. Not even Lee Marvin’s Sgt Possum in Samuel Fuller’s The Big Red One, another knife killer, went quite so far.

Don Evans, a World War II tank gunner who advised Ayer, now cautions that some scenes in Fury are more extreme than what he witnessed in 28 months overseas. “I don’t recall anyone having to kill a buddy,” Evans said in a phone interview.

Yet the portrayal is grounded in years of research. “He had every type of camouflage and weapons and uniforms,” said John Lesher, another of the film’s producers, about Ayer.

Through all of it, Ayer learned what some who had made a deep study of the so-called Greatest Generation already knew: American fighters were not saints. Tom Brokaw, who wrote a book by that title, remembers being told by one veteran, “After the Germans killed my brother, I never took another POW alive.”

Fury, which cost about $80 million, was mainly shot in Britain. Access to tanks was a prime consideration: Vintage Shermans were more readily available there. Plus, the production was permitted to use a rare Tiger tank, lent by the Tank Museum in Bovington.

The principal actors were considerably roughed up before filming began. Pushed by the military consultants, they spent a week on a bivouac in England — no shaves, no showers, no plumbing — learning to handle the grimy side of soldiering.

The cast, Bernthal said, was pushed by Ayer to behave as if “this was the last movie you were ever going to make”.

Pitt’s decision to take the role of Wardaddy was a sudden one. Early last year, he read the script during a quick trip to Europe, and, on returning, immediately jumped in.

Apparently, it mattered not that Pitt’s partner, Angelina Jolie, is directing a very different World War II story, Unbroken, which will soon be competing with Fury on the awards circuit. A third drama set during the war, The Imitation Game, starring Keira Knightley and Benedict Cumberbatch, is also expected to set an awards push from The Weinstein Co.

One near hitch in the deal making: QED, which is backed by Russian investors Sasha Shapiro and Anton Lessine, initially found it difficult to sell rights in Russia. Distributors were wary of a project that portrayed Americans on a push toward Berlin, which, after all, was taken by Soviet troops.